Incandescent electric lamp and basing cement



0d. 19430 E. RISCHMID 2,332,116

INCANDESCENT ELECTRICLAMP AND BASING CEMENT Filed May 3, 1941.

INVENTOR E z. .so/M/p.

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ATTORNEY Patented Oct. 1 9, 1943 INCANDESCENT nmc'rmc LAMP AND mismc CEMENT Edward Robert 'Schmld, Verona, N. J., assignor to Westinghouse Electric Company, East Pittsburgh, Pa,

of Pennsylvania & Manufacturing a corporation Application May 3, 1941, Serial No. 391,639

2 Claims.

This invention relates to incandescent electric lamps normally operated in series, and more particularly to a lamp having means incorporated therewith for permitting current to bypass upon failure of its tinguishment of a lamp or lamps with.

The principal object of my invention, generally considered, is to provide an incandescent electric lamp of the series type, such as may be filament, thereby avoiding exin series there used for Christmas tree decoration, and incor-' porating therein a basing cement which automatically becomes conducting only upon an increase in the voltage normally applicable thereto, as upon failure of the lamp filament when operating in series with another or other lamps, thereby preventing said other or others from extinguishment.

Another object of my invention is the provision of a cheap series Christmas tree lamp, comprising a, bulb with a base secured thereto by cement which normally functions as an in-- sulator, but which is adapted to bypass current upon failure of the lamp filament and thereby prevent extinguishment of other lamps in series therewith.

A further object of my invention is the provision of a double-function basing cement or one which normally serves only as means for securing the base to, the bulb of a series lamp, but which upon an increase in the applied voltage, as when the filament fails during operation in series with other devices, becomes, conducting and bypasses current directly between external portions tinguishment of said associated devices.

A still further object of my invention is the provision of a basing cement for incandescent electric lamps which is an insulator for practical purposes at low or normal voltages and a conductor of substantial current at higher or abnormal voltages.

Other objects and advantages of the invention,

relating to the particular arrangement and construction of the various parts, will become apparent as the description proceeds.

Referring to the drawing, an enlarged elevational view, partly in axial section, of an incandescent electric lamp embodying my invention.

It has heretofore been found that when using a plurality of lamps connected in series, great inconvenience occurs upon the failure of one of the lamps owing to a broken filament or other cause,-since such failure breaks the continuity of .the circuit and the rest of the lamps are extinguished.

Inasmuch as it is difilcult to determine by inspection which lampis defective, especially if the bulbs thereof are coated, it becomes necessary,

of lead-in-conductors to prevent exthe single figure is i in order to pick out thefailure, to test by trial until thedefective lamp has been discovered.

This procedure involves time and inconvenience and has heretofore caused considerable an- 5 noyance in connection with lamps such'as those employed for decorating Christmas trees.

In accordance with the present invention, I provide a form of lamp ill of the series type, such as shown in the drawing, comprising a bulb Ii and a conductive base shell l2, desirably formed of brass, enclosing and secured to a portion 22 of said bulb by cement i3. 4

The lamp illustrated is one of the type generally used for Christmas tree decoration and may be burned in series with seven other similar lamps from a domestic lighting circuit of 110-120 volts, although I do not wish to be limited'to this, as more, such as twenty, or less may be connected in series.

The lamp, in accordance with my invention, is so constructed that if the filament M breaks or burns out, the other lamps of the series continue to operate by virtue of the cement it becoming substantially conductive. Essentially 5 such cement comprises an insulating binder, such as shellac, Durite (which is a phenol furfural condensate, much like Bakelite) or Bakelite,

a filler of finely divided conducting material, such as aluminum, iron, galena or graphite, and a solvent such as alcohol to make a paste.

It will, therefore, be seen that the cement is produced by replacing the usual inert filler materials, such as marble flour, ground mineral barytes, titanium oxide and the like by graded 5 finely-divided particles of conductivefillers, such as those above mentioned, which have correct electrical breakdown characteristics.

The basing cement is desirably prepared in the conventional manner and the baseis pre-filled and baked according to standard practice.

In the case of series lamps of the Christmas tree type, the special cement should maintain the circuit as the first two or three lamps burn out. If these burnouts are not properly replaced the remaining lamps will automatically burn out quicker than under normal conditions, the burn out time depending on the type of cement used. When the last lamp burns out, if one is-careless enough to let the string go that far, the circuit is opened within the cement by melting of a lead,

' or as a last resort by the blowing of a fuse.

It has been breakdown voltage over a wide range by controlling the particle size of the conducting powder, which is desirably aluminum, diluting it with definite percentages of inert fillers, such as mineral barytes, or by varying the ratio of cement resins to the conductive powder.

It will, therefore, be seen that in accordance with my invention the cement body, in addition only then i found possible to vary the cement to its function as a cementing medium to fasten the lamp bulb to the base, also serves as a conductor of electric current between the eyelet lead and the base shell under designed electrical conditions.

The rupture of the lamp filamentand the consequent increase in voltage is the usual condition under which the cement functions as a conductor. The combination of conducting and nonconducting substances is so adjusted that the non-conducting film of oxide, for example, which may be on the aluminum powder, if such is used, is punctured when the voltageacross the cement medium is increased.

For the non-conductor or hinder, I may use resins, gums, glues, waxes, asphalts, or other organic or inorganic binders and adhesive media. For the conductor or filler I may use the metals, the metal oxides or other metal compounds, such as galena, or nonmetallic substances, such as graphite.

The conductivity of the above materials in the cement mixture varies widely and many combinations are possible to obtain specially desired results. Particle size of the filler or conductor exerts an effect, both to increase and decrease the breakdown voltage. With some materials, such as the metal oxides, breakdown voltage increases with particle size while with some metals a contrary effect is produced. Electrically insulating materials, such as marble dust, boric acid, or carbon dioxide producing compounds, may be added to increase the breakdown voltage or quench the are which might be formed.

Some of the properties that may be developed with a change of materials are as follows:

1. Low melting point cement may be provided to interrupt the circuit.

2. Materials with arc-quenching properties may be employed to minimize fire hazards.

3. Some materials have sufiicient resistance, even when their insulating property has been overcome, to reduce the over-voltage on residual lamps and prevent charring of the coating when such lamps burn at over-voltage.

4. Breakdown voltages may be varied by choice of materials and their ratio in a combination.

5. The cement may have a high melting point in order to avoid the development of short circuits which may occur, as when thermoplastic binders in the cement soften slightly on continuous burning and reduce the space relation, as by a lead wire expanding toward the base.

I will now describe in detail three of several formulae which have been used successfully to produce basing cement having the desired properties.

Formula No. 1

Parts by weight Orange shellac (as an example of thermoplastic resins) 20 Aluminum powder (as an example of metallic filler), about 80 Alcohol (as an example of a solvent) suflicient to form a workable paste or cement.

The above formula has been used to produce a large number of lamps called detectolite lamps.

The aluminum used was manufactured by the Metals Disintegrating Company process, as distinguished from flake aluminum. Aluminum represents a type of metal powder characterized by having a thin non-conducting oxide layer on each conducting metal particle. When this oxide Formu la No. 2

. Parts by weight Durite resin (as an example of thermosettirig resin) -l 25 Aluminum powder, about 75 Alcohol-suflicient to form a workable paste or cement.

The above formula has been used to manufacture even more lamps than the first-mentioned formula. The aluminum powder characteristics are the same as in Formula No. 1. This cement performs very well as a short-circuiting medium, its only apparent weakness being tendency to are through the brass shell, but only if burnout lamps are not replaced, and when the filament of the last lamp in the string fails. It is, therefore, desirably protected by a fuse, reference being had to the concurrently filed application of Hageman and Tully, Serial No. 391,650, entitled Incandescent electric lamp with base fuse, and owned by the assignee of the present application.

Formula No. 3

Alcohol-sufficient to form a workable paste or cement.

This is an example of a cement of the resistor or rheostat type. A portion of the electrical energy, after failure of the filament during operation, is constantly dissipated in the body of the cement. As a result of this action, longer life is obtained from the remaining lamps in the string, even if burnouts are not replaced promptly.

Galena is a filler which prevents arcing through the base shell when a thermosetting resin is used. Best results have been obtained from 325 mesh galena.

For ten parts of "Durlte, the galena must be held to 55 plus or minus 5 parts (551-5 parts) to give satisfactory performance, above 60 parts, too many lamps short through the base before filament failure, while below 50 parts, too many lamps fail to function as their filaments burn out.

The preferably tungsten filament I4 is, in the present embodiment, supported upon a mount i5, comprising lead-in conductors l6 and I1, passing through a glass bead l8, and with their inner ends secured to the ends of the filament, as indicated at l9 and 2|.

The opposite ends of the conductors l6 and I! pass through the portion 22 of the bulb which is embedded in the basing cement I3. The lead I! passes through said cement and is secured, as by soldering, to the preferably brass base shell l2, as indicated at 23. The other lead is passes through the portion 22 of the lamp bulb assarie into the basing cement I3 and from there continues to the base eyelet 24, insulated from the conducting or brass shell I2 by means 25, such as a customary black glass.

From the foregoing it will be seen that I have devised a lamp of the series type which maintains other lamps of the string operating, even after failure of its filament, by short-circuiting basing cement which becomes substantially conducting only upon increase in voltage, as

under such circumstances.

Although preferred embodiments of my inven- -tion have been disclosed, it will be understood that I am not limited to the number and kind of lamps in series or the exact composition of the short-circuiting basing cement, as variations of 1 any feature or features may be made, and such variation may be accompanied by a corresponding variation of another feature or features, if considered desirable. Therefore, modifications may be made within the spirit and scope or the appended claims.

I claim:

1. An incandescent electric lamp comprisin a bulb, a mount with a filament disposed in said bulb and leads projecting therefrom, a base receiving a portion of said bulb and including a conductive shell and a contact member insulated therefrom, one of said leads being connected to said contact member and the other to said shell, and basing cement disposed between the peripheral portion of said shell and the received portion of said bulb for securing said parts together, said cement enveloping portions of.

said leads and comprising a mixture of 25 parts by weight of a thermo-setting phenol furfural resin, about '75 parts by weight of 300 mesh aluminum powder, and alcohol sufficient to form a workable paste.

2. A basing cement comprising 25.partsby weight of a theme-setting phenol furfurai resin, about 75 parts by weight of 300 mesh aluminum powder, and enough alcohol to make a workable paste.

I EDWARD ROBERT SCHM'ID. 

